26 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



the resulting system of drainage is, it would have been still more 

 so had Rocky River when ponded overflowed at the head of its 

 western instead of its eastern fork, taken its way past Sherman 

 into the Housatonic near Gaylordsville, and discharging at this 

 point lost the advantage of the fall of the Housatonic 'between 

 Gaylordsville and Boardman. 



In glaciated regions an area of swamp land may be taken as 

 an indication of interference by the glacier with the natural run- 

 off. The swamp in which Wood Creek joins the upper fork of 

 Rocky River (fig. i), was formerly a lake due to a dam built 

 across the lower end of a river valley. Although the ponded 

 water extended only a short distance up the steeper side valleys, 

 it extended several miles up the main stream. The whole area of 

 this glacial lake, except two small ponds and the narrow channels 

 through which the river now flows, has been converted into a 

 peat-filled bog having a depth of from 8 to 45 feet. 1 



At the termination of the swampy area on the eastern branch 

 of Rocky River no indication is found of a dam such as would 

 be required for so extensive a ponding of the waters. Here the 

 valley is very narrow, and though the river bed is encumbered 

 with heavy boulders, rock outcrops are so numerous as to pre- 

 clude the idea of a drift cover raising the water level. This is 

 just the condition to be expected if Rocky River reached its 

 present outlet by overtopping a low col .at the head of its former 

 eastern branch. 



The southern end of the Neversink Pond valley is the only 

 other place whose level is so low that drift deposits could have 

 interfered with the Rocky River drainage. The moraine at the 

 head of this valley, crossing the country some two miles north of 

 the city of Danbury and binding together two prominent north- 

 and-south ridges, was evidently the barrier which choked the 

 Rocky River valley near its mouth and turned back the preglacial 

 river. 



When Rocky River was thus ponded its lowest outlet was 

 found to be at the head of its eastern fork. Here the waters 

 spilled over the old divide and took possession of the channel of 



'Report of soundings made in 1907 by T. T. Giffen. 



